Harrison's Internal Medicine Part 2. Cardinal Manifestations and Presentation of Diseases Section 9. Alterations in the Skin Chapter 53. Eczema, Psoriasis, Cutaneous Infections, Acne, and Other Common Skin Disorders Eczema and Dermatitis
Eczema and Dermatitis: Introduction
Eczema is a type of dermatitis and these terms are often used synonymously (atopic eczema or atopic dermatitis). Eczema is a reaction pattern that presents with variable clinical findings and the common histologic finding of spongiosis (intercellular edema of the epidermis).

Lichen Simplex Chronicus Lichen simplex chronicus may represent the end stage of a variety of pruritic and eczematous disorders, including atopic dermatitis. It consists of a circumscribed plaque or plaques of lichenified skin (thickening of the skin and accentuation of normal skin markings) due to chronic scratching or rubbing. Common areas involved include the posterior nuchal region, dorsum of the feet, and ankles. Treatment of lichen simplex chronicus centers on breaking the cycle of chronic itching and scratching.

Figure 53-1
Atopic dermatitis.
Hyperpigmentation, lichenification, and scaling in the antecubital fossae are seen in this patient with atopic dermatitis. (Courtesy of Robert Swerlick, MD; with permission.)
Atopic Dermatitis: Treatment Therapy of AD should include avoidance of cutaneous irritants, adequate moisturizing through the application of emollients, judicious use of topical antiinflammatory agents, and prompt treatment of secondary infection. Patients should be instructed to bathe no more often than daily using warm or cool water, and to use only mild bath soap.

Dyshidrotic eczema. This example is characterized by deep-seated vesicles and scaling on palms and lateral fingers, and the disease is often associated with an atopic diathesis.
The evaluation of a patient with hand eczema should include an assessment of potential occupation-associated exposures. The history should be directed to identifying possible irritant or allergen exposures.

Eczema is a type of dermatitis and these terms are often used synonymously (atopic eczema or atopic dermatitis). Eczema is a reaction pattern that presents with variable clinical findings and the common histologic finding of spongiosis (intercellular edema of the epidermis). Eczema is the final common expression for a number of disorders, including those discussed in the following sections. Primary lesions may include erythematous macules, papules, and vesicles, which can coalesce to form patches and plaques.

Several new aspects have been
highlighted: for example, a novel role for lipids as receptors which drive protein
sorting, the diversity of the sorting events that occur at the level of the Golgi
apparatus, and the cross talk between exocytosis and autophagy. Moreover, an
interesting example of how the knowledge of these pathways is exploited to generate
novel secretory routes to direct the synthesis of bio-molecules in “cell factories” is
discussed.

In the five years since the first edition of this book was published, there has been an explosion
in new information relating to the nature of dry skin and its treatment. Investigators from various
disciplines, including dermatologists, pharmacists, chemists, biochemists, molecular biologists,
physiologists, pharmacologists, and even psychologists have advanced our knowledge tremendously.
We now understand that the stratum corneum has a surprisingly large number of functions in maintaining
the physiologic stability and homeostasis of the skin and mind.

It has long been noted anecdotally that affect, psychological
state and neurologic state have influences on
inflammatory skin diseases. Disorders such as psoriasis,
atopic dermatitis, acne and rosacea, among many
others, are reported to become exacerbated by stress.
Furthermore, it is widely believed that stress alters
cutaneous immunity. However, mechanisms responsible
for these effects have remained incompletely
understood. Scientific evidence for an influence of
the nervous system on immune and inflammatory
processes in the skin has been developed only relatively
recently.